Chemistry

Primary batteries cannot be recharged and are
constructed of alkaline, zinc air, or zinc carbon materials.

Secondary batteries are rechargeable and are
constructed of lead acid, nickel cadmium, nickel metal hydride, lithium
and lithium-ion. New chemistry's are being developed everyday. Lead
acid batteries have been used in cars and trucks for almost 100 years.
They are designed to start a vehicle, giving a large current flow for
20 or so seconds, then accept a charge from the alternator to recharge
the battery. A deep cycle lead acid battery is designed to produce a
lower current draw for a long period of time, then be recharged at a
lower current for a longer period of time. These batteries are used
in golf carts and fishing boats. They have thicker plates and a dense
oxide paste. A 12 volt lead acid battery should never be discharged
below 10.5 volts and under no circumstances should a lead acid battery
be left in a discharged state. This will cause the plates to sulfate
and kill the battery.

Sealed lead acid batteries are also called valve
regulated batteries. They are sealed so that the electrolyte will not
leak when the battery is turned up side down but have valves that open
to release gases if the battery is overcharged or misused in some fashion.
Once the valves have been opened, the life of the battery is effected.

Gell cell batteries are much like sealed lead
acid. They are sealed and have valves but the electrolyte is a gell
rather than a liquid. Gelled batteries usually do not have as high an
amperage rating as the same sized sealed lead acid battery.

Nickel cadmium technology is older and known
for its "memory effect". True memory effect rarely occurs in consumer
devices because it requires many cycles to precisely the same states
of charge and discharge. Most failures in consumer devices occur because
of overcharging and or heat. Don't completely discharge packs every
time to avoid memory effect. Discharging a pack too far can cause the
stronger cell(s) to charge the weakest cell in the opposite direction.
This is called reverse charging and will lead to a very early death
of the pack. However, through normal use, it's fine to occasionally
run the devise to the point where it indicates a low battery. NiCds
that are weak due to overcharging can sometimes be rejuvenated by a
full charge/deep discharge cycle. Unfortunately, the only way to assure
that reverse charging doesn't occur is to discharge each cell separately.
With proper operating procedures and maintenance, and average nicad
battery will last between 1000 to 1300 cycles.

Nickel-metal hydride batteries have approximately
30 to 80% more capacity than nicad and no memory effect. NiMH batteries
perform better on low discharge rates than nicads and are preferred
in small portable devices because they give longer run times. They also
take less time to recharge. Follow your manufacturers instructions on
charging. To prolong the life of the battery pack, remove it from the
devise and charger when not in use and store it in a dry, cool place.
Do not run the battery completely dead or discharged. Fully charged
batteries discharge rapidly even when not in use. Recharge prior to
use.

Lithium and Lithium-Ion batteries are expensive
compared to nicad and NiMH but worth the money if you need their performance.
These batteries have higher output but lower weight. If exposed to extreme
cold (below 50 F), the effective operational time decreases significantly.
Exposure to temperatures below 32 F will render the battery inoperative.
Charge the battery pack at least once every six months. Do not leave
the battery pack being charged for long periods of time. Be careful
to never puncture these batteries as they might explode if air gets
inside.